1. Field of the Invention
This invention relates generally to lamps having concave reflectors and particularly to discharge lamps having compound, concave reflectors.
2. Background Art
Lamps having one or more concave reflectors to reflect light from a small source along a longitudinal axis are known in the art. A reflector lamp of this general structure has been disclosed, for example, in European Patent EP 1 076 203 A2 to Lieszkovszky. The reflector lamp disclosed includes a first surface area having a paraboloid, an ellipsoid or a spheroid configuration and a second surface area having a paraboloid configuration. The second surface area has a fluted configuration, and the surface areas distribute light to minimize centralized hot spot effects and to direct light in a near-parallel manner along a longitudinal axis within a light cone preferably having a maximum apex angle of 5 degrees.
Similar reflector lamps that use a discharge lamp for a light source have a disadvantage, however. When such a lamp is disposed in near-horizontal orientations, a portion of emitted light passes through a typically yellow condensate formed of vapor condensed near a colder, low side within the discharge lamp. The condensate absorbs blue light, and the remaining emitted light is predominantly yellow. Since the yellow light is not radiated evenly about the longitudinal axis, it will not be distributed evenly across a surface being illuminated.